Ex-"e" and Ex-"n" MV Motors

[davva]

I'm new to the petrochem industry and i'm getting my head around requirements for equipment in hazardous areas.

I would like to know if it is necessary to purge MV motors prior to start. I have been informed that it is a requirement to purge Ex"n" classification MV motors and have been asked to investigate whether it is a requirement to purge Ex"e" MV motors prior to start.

I have looked at IEC60079 parts 7 and 15 for Ex"e" and Ex"n" equipment but neither seems to specifically state this requirement. Reference is made to IEC60079-2 (pressurised appartus) but I do not have access to this standard at the moment and will take a few days to get it.

Any help would be greatly appreciated.

 

[davva]

Since posting the above I have found relevant statements in pt7 and pt 15 of IEC60079.

 

[magneticted]

Hi davva, this is an emotive issue this days, EN60079-15:2005 (EExnA )refers to a risk assessment which has to be completed by the motor manufacture and the end user. Their are assigned tables and basically if the stator or rotor risk factor is above 6 or 5 respectively then either the motor manufacturer has either to conduct stator and rotor type test in a gas environment ( IIB/IIC )or provide the machine with pre start purging flanges.This applies to machines above 1kv. Therefore it is required to provide this arrangement where necessary and is mandotary for motors being supplied in the EU (Atex ) Outside the EU,it is not mandotary, IEC60079-15 ExnA but strongly recommended. However ABB Helsinki for their range of Ex motors have obtained a gas certificate, which states these motors have passed a stator and rotor type test in gas. The certificate shows the stator has passed in gas group IIC up a nominal vlotage 9.5Kv, and gas group IIB up to a nominal voltage of 11.5kv.Hence the need for pre start purging disappears if using an ABB motor within the range described in the certificate, and assuring the end user of proven safety